♻️ Refactor global_id_column to flow through ActiveSupport's class_attribute

This simplifies the implementation's API substantially by defining both
instance and class methods, and rails/globalid already depends on
ActiveSupport

Author: tylerwillingham

lib/global_id/identification.rb

@@ -1,3 +1,5 @@
+require "active_support/core_ext/class/attribute"
+
 class GlobalID
   # Mix `GlobalID::Identification` into any model with a `#find(id)` class
   # method. Support is automatically included in Active Record.
@@ -27,17 +29,7 @@ class GlobalID
   #   # => #<Person:0x007fae94bf6298 @id="1">
   module Identification
     def self.included(base)
-      base.extend(ClassMethods)
-    end
-
-    module ClassMethods
-      def global_id_column(column_name = nil)
-        @global_id_column ||= column_name
-      end
-    end
-
-    def global_id_method
-      self.class.global_id_column || :id
+      base.class_attribute :global_id_column, default: :id, instance_writer: false
     end
 
     # Returns the Global ID of the model.

lib/global_id/locator.rb

@@ -162,10 +162,10 @@ def locate(gid, options = {})
           model_class = gid.model_class
           model_class = model_class.includes(options[:includes]) if options[:includes]
 
-          if model_class.global_id_column
-            model_class.find_by model_class.global_id_column => gid.model_id
-          else
+          if model_class.global_id_column == :id
             model_class.find gid.model_id
+          else
+            model_class.find_by model_class.global_id_column => gid.model_id
           end
         end
 

lib/global_id/uri/gid.rb

@@ -72,7 +72,7 @@ def parse(uri)
       #
       #   URI::GID.create('bcx', Person.find(5), database: 'superhumans')
       def create(app, model, params = nil)
-        build app: app, model_name: model.class.name, model_id: model.send(model.global_id_method), params: params
+        build app: app, model_name: model.class.name, model_id: model.send(model.global_id_column), params: params
       end
 
       # Create a new URI::GID from components with argument check.

test/models/configurable_key_model.rb

@@ -6,7 +6,7 @@ class ConfigurableKeyModel
 
   attr_accessor :id, :external_id
 
-  global_id_column :external_id
+  self.global_id_column = :external_id
 
   class << self
     def primary_key